A crossbar switch is a fundamental unit of many communications networks, ranging from telecommunications to computer interconnects. In the most general form of a crossbar switch, each of N inputs may be connected to any number of N outputs. In the most common implementation, the input-output connection is one-to-one, that is, one input goes to exactly one output.
Electronic implementations of a crossbar switch can be quite simple and monolithic at low data rates. In the typical configuration of an electronic crossbar switch, N inputs are directed into a matrix of N.sup.2 switches that connect the inputs to the N outputs. While each of the N.sup.2 switches requires its own control line, in practice each switch would be equipped with a memory element so that they need not be programmed simultaneously. In practice, the switches are programmed through some type of multiplexed addressing scheme.
The limitations of electronic crossbar switches become significant as data rates climb into the gigabit regime, bringing with it problems of crosstalk, propagation delay, and waveform dispersion. Furthermore, these prior art switches grow enormously in physical size and power considerations as data rates increase.
It is precisely in the gigabit regime where optical data paths begin to show superior performance. An optical implementation of the same crossbar switch is in principle possible. Techniques for optical generation, modulation, and detection are now well-developed. What has been missing up to now is the matrix switch array incorporating high density, good contrast, and built-in memory.
Thus, improved crossbar switches are required to handle data rates in the gigabit regime.